Frederick Ayertey

Malaria and trypanosomiasis are protozoan diseases which pose a devastating challenge to human health and productivity especially, in Africa where their respective vectors (female Anopheles mosquito and tsetse fly) abound. Various medicinal plants are used to treat these parasitic diseases. However, the scientific basis of their use and toxicological profiles have not been assessed. We have, therefore, evaluated the antiplasmodial, antitrypanosomal, and cytotoxic activities of four African medicinal plant extracts namely, Anthonotha macrophylla leaf (AML), Annickia polycarpa leaf (APLE), Tieghemella heckelii stem bark (THBE), and Antrocaryon micraster stem bark (AMSBE) extracts in vitro against P. falciparum (W2mef laboratory strain), T. brucei (GUTat 3.1 strain), and mammalian RAW 264.7 macrophage cell line, respectively. The most active antiplasmodial extract was AML (IC₅₀=5.00.08μg/mL with SI of 21.9). THBE also, produced the most effective antitrypanosomal activity (IC₅₀=11.00.09μg/mL and SI of 10.2) among the extracts. In addition, none of the extracts produced toxic effect in the RAW 264.7 macrophage cell line except APLE which was moderately cytotoxic and also produced the least SI in both antitrypanosomal and antiplasmodial assays. These results suggest that AML and THBE could offer safe and alternative therapy for malaria and trypanosomiasis. This is the first study to report the antitrypanosomal and in vitro antiplasmodial activities of these four plants/plant parts. The cytotoxicity of the plant parts used is also being reported for the first time except for the T. heckelii stem bark.

In the absence of vaccines, there is a need for alternative sources of effective chemotherapy for African trypanosomiasis (AT). The increasing rate of resistance and toxicity of commercially available antitrypanosomal drugs also necessitates an investigation into the mode of action of new antitrypanosomals for AT. In this study, furoquinoline 4, 7, 8-trimethoxyfuro (2, 3-b) quinoline (compound 1) and oxylipin 9-oxo-10, 12-octadecadienoic acid (compound 2) were isolated from the plant species Zanthoxylum zanthoxyloides (Lam) Zepern and Timler (root), and their in vitro efficacy and mechanisms of action investigated in Trypanosoma brucei (T. brucei), the species responsible for AT. Both compounds resulted in a selectively significant growth inhibition of T. brucei (compound 1, half-maximal effective concentration EC₅₀ = 1.7 μM, selectivity indices SI = 74.9; compound 2, EC₅₀ = 1.2 μM, SI = 107.3). With regards to effect on the cell cycle phases of T. brucei, only compound 1 significantly arrested the second growth-mitotic (G2-M) phase progression even though G2-M and DNA replication (S) phase arrest resulted in the overall reduction of T. brucei cells in G0-G1 for both compounds. Moreover, both compounds resulted in the aggregation and distortion of the elongated slender morphology of T. brucei. Analysis of antioxidant potential revealed that at their minimum and maximum concentrations, the compounds exhibited significant oxidative activities in T. brucei (compound 1, 22.7 μM Trolox equivalent (TE), 221.2 μM TE; compound 2, 15.0 μM TE, 297.7 μM TE). Analysis of growth kinetics also showed that compound 1 exhibited a relatively consistent growth inhibition of T. brucei at different concentrations as compared to compound 2. The results suggest that compounds 1 and 2 are promising antitrypanosomals with the potential for further development into novel AT chemotherapy.

Mist Antiaris is a herbal decoction for treatment of nervous disorders. Safety and efficacy were evaluated in Sprague-Dawley rats and human patients, respectively. Acute toxicity was assessed by administration of a single 5000 mg/kg oral dose of decoction to a group of six rats. For subchronic toxicity, four groups of six rats each received water (control) or 10, 100, or 200 mg/kg oral doses of decoction daily for eight weeks. Body weight, serum, urine, and hematological profile of the animals in each group were monitored over the period. Effects of treatment on pentobarbital-induced sleeping time and histology of liver, lung, heart, and kidney tissue were assessed at the end of the study. There was no evidence of acute toxicity within 48 hours of the oral dose. Over the 8-week period, body weight increases in Mist Antiaris treatment groups were reduced relative to the control group. There were no significant differences in urine profile, serum biochemistry, hematological parameters, and pentobarbital-induced sleeping time. Tissue histology revealed no differences relative to controls. Assessment of efficacy was by retrospective review of data on patients who presented with peripheral neuropathy. Treatment resulted in 53.7 % of patients reporting complete resolution and 15.7 % showing reduction in neuropathic symptoms. The data demonstrate that there is no toxicity due to subchronic administration of Mist Antiaris in Sprague-Dawley rats. The reduction or resolution of neuropathic symptoms indicated by patents’ file data provides evidence to suggest that Mist Antiaris has antineuropathic effects.